I've never indulged in bumper stickers, but if I could find one that said "Hang up and DRIVE" I might slather that on the Grace car, though I wonder if the term "hanging up a phone" is too dated for the generation who may never have HAD a phone that you can hang up?
In the days when my friends had cell phones and I didn't, I got freaked out every time they'd call me from a moving car they were driving, worrying about their safety. Now that I've joined the cellphone crowd, I feel guilty using the phone IN the car, even when I'm parked. I still tell 'em if they call while they are driving "call me back when you stop the car, please"
The proliferation of cellphone use among the young seems to have unfortunately coincided with a severe decline in manners and the discarding of social mores that seem common sensical to me. Rudeness rules the day in so many more ways than just cellphone usage in inappropriate places/audiences. Driving while on a cellphone is a good way to show Darwinian principles - I just hoping that the innocent don't get taken along in the crash.